The present invention relates generally to a magnetic bubble device and more particularly to a magnetic bubble device which includes magnetic bubble propagation tracks formed through ion implantation and which enjoys a wide operation margine and a stabilized operation.
Among the magnetic bubble propagation tracks formed through ion implantation, there is known bubble propagation tracks of a meandering or undulated pattern, as is disclosed in "Bell Syst. tech. J.", Vol. 59, p. 229 (1980).
As schematically shown in FIG. 1, a magnetic bubble device is generally made up of a plurality of minor loops 2 for storing therein information and a major line or major loop for reading and writing information. Various parts 4 such as a transfer gate, a swap gate and a replicator are used at connecting portions between the minor loops 2 and the major line (or major loop). The minor loops 2 are formed of bubble propagation tracks, and occupy most of the area of the magnetic bubble device. The major line (or major loop) is made up of bubble propagation tracks 10 and 12, a bubble generator 6 and a detector 8. The minor loops 2 are connected to the major line (or major loop) through the parts 4 such as the transfer gate, the swap gate and the replicator. Although only two minor loops are shown in FIG. 1, it is needless to say that the magnetic bubble device is actually provided with a large number of minor loops.
FIG. 2 shows a configuration or pattern of the propagation tracks which constitute the minor loop. In FIG. 2, a reference numeral 14 denotes a region in which an inplane magnetization layer is formed on the surface of a magnetic bubble material through ion implantation, 16 denotes a region in which the inplane magnetization layer is absent or alternatively an inplane magnetization layer shallower than that of the region 14 is formed, and 18 denotes a magnetic bubble. The illustrated propagation tracks are destined to constitute the minor loops at a period or pitch P of 8 .mu.m. It has been found that a problem arises when the minor loop is to be realized by the propagation tracks of the meandering or undulated configuration at the pitch of 4 .mu.m or less. More specifically, when the propagation tracks of a cell size of 4 .mu.m.times.4 .mu.m are formed, there arises a problem that slight variation in an amplitude W possibly brought about in the patterning will involve a large variation in the operation margin of the bubble device. This can be explained by the fact that because of the reduced gap between the propagation tracks, erroneous operation is produced by the unwanted transfer of the bubble to the adjacent track.